This invention relates to the art of handle covers and, more particularly, to an adjustable handle cover to accommodate a range of hand spans.
The present invention finds particular utility in producing an ergonomic connection between a hand tool with a two handle configuration and the user's hand, and accordingly, is disclosed and described in detail hereinafter in connection with such use. However, it will be appreciated that the invention is applicable to use in connection with other handle configurations.
Ergonomics is the study of human capability and psychology in relation to the working environment and the equipment operated by the worker. As applied to hand tools, ergonomics relates to the use of the human hand to produce the forces required to operate the hand tool. Furthermore, ergonomics relates to designing hand tools that require less hand force to operate and reduce fatigue, injury or damage caused by long term repetitive use.
The industry has begun to design hand tools that better conform to the human hand. In consideration of the large range in sizes of the human hand, it has been difficult, if not impossible to produce a hand tool that is ergonomic to all users. One handle configuration is not capable of ergonomicaly conforming with a wide range of hand spans. Accordingly, attempts have been made to address multiple hand spans, but none have produced a cost effective product line that meets the needs of the end user.
One method of addressing multiple hand spans is to create a tool in a plurality of sizes. For instance, a small sized tool would be produced from handles designed for a small hand span while a large sized tool would be produced from handles designed for a larger hand. The result of this method is high inventory costs and the reduced ability to accommodate the end user. Even though one size may out perform other sizes, all sizes must be inventoried to accommodate the end user having either very small or very large hand spans.
In order to better service the end user and reduce inventory costs, attempts have been made to utilize a single handle design to accommodate a range of hand spans. One method has been to produce a handle that conforms with one particular hand span and then utilize mechanical means to reform the shape of the handle so that it will conform to other hand spans. This method requires an additional operation to produce handle spans of differing sizes which typically includes physically bending at least one handle. Operations such as these must be performed under controlled circumstances thereby preventing adjustment by the end user. While this method can reduce inventory costs by allowing one size to be inventoried, it lengthens the lead time between order and delivery by adding an operation. Furthermore, once a tool has been formed to a special handle span, it cannot be subsequently changed, thereby reducing flexible manufacturing techniques.
Another method is to produce handle blanks to conform with only the largest hand span and then smaller hand spans are accommodated by varying the amount of material that is removed from the working or cutting edge of the tool's jaw. More particularly, as more material is removed from the working surface of the jaw, the smaller the handle span becomes. While this method also allows one pair of handles to accommodate multiple handle spans, it requires additional and more complex metal removal steps to produce the desired handle span. This not only increases the cost associated with manufacturing the tool, but also increases the lead times and inventory costs associated with reacting to the needs of the end user.
Another method of addressing multiple hand spans is to use special pivot hardware. This method can include the common slip joint pivot. This joint includes one handle with a plurality of pivot slots or openings and the other handle with pivot hardware designed to selectively engage each of these slots or openings. A pivot such as this allows adjustment of the handle span based on which slot or opening is utilized. While this method allows for the end users to adjust the handle span based on their needs, it is costly to produce, the pivot area is very large, and the pivot joint can inadvertently become misadjusted during use. While this approach is satisfactory for pliers, it does not work with cutting tools where the jaws must close. These attributes create a tool that is expensive and difficult to use.
In an effort to address the shortcomings of the slip joint tool, tools have been designed to include a slip joint pivot that automatically adjusts the handle span. While this reduces the clumsiness of the tool and eliminates the need to choose the proper pivot slot each time the tool is used, the pivot area remains very large, expensive and complex in design. Furthermore, while both the standard and the automatic slip joint tools can be utilized to meet the needs of a range of hand spans, they are not well adapted for repetitive use by the end user.